A greenhouse is a building where plants are grown. These structures range in size from small sheds to very large buildings. A miniature greenhouse is known as a cold frame. A greenhouse is a structure with different types of covering materials, such as a glass or plastic roof and frequently glass or plastic walls; it heats up because incoming visible solar radiation (for which the glass is transparent) from the sun is absorbed by plants, soil and other things inside the building. Air warmed by the heat from hot interior surfaces is retained in the building by the roof and wall. In addition, the warmed structures and plants inside the greenhouse re-radiate some of their thermal energy in the infrared, to which glass is partly opaque, so some of this energy is also trapped inside the glasshouse. However, this latter process is a minor player compared with the former process. Thus, the primary heating mechanisms of a greenhouse is convention. This can be demonstrated by opening a small window near the roof of a greenhouse; the temperature drops considerably. This principle is the basis of the autovent automatic cooling system.
This book is written in simple, easy to understand language which will be highly useful to the students, teachers, extension personnel, scientists and progressive horticulturist.
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